I have a new home with a dual fuel, dual zone HVAC system, which supplies the main living level (zone 1) and a daylight basement (zone 2). They are seperated by a door at the top of the stairs. When the unit is supplying the main level, we have to leave the door open at least four or five inches, or it gets sucked closed with a bang! The air handler is using the basement returns to feed the air requirements.

I spoke to two seperate heating/cooling guys (from the same shop who installed the system) and both said that this is normal, that the air from both floors needs to mix. This makes sense I guess if I wanted to keep both floors conditioned, but the basement tends to stay at a comfortable temp, and we're down there rarely anyway. Seems to me this is an imbalanced system design. Am I correct, or am I the one imbalanced? :eek:

I'd also be interested in any thoughts on easily correcting this - maybe a simple pass-through register from the main level to the basement? The door in question is 90* from another door to our garage (they open into each other), which means making sure they don't bang into each other, so it would be nice to be able to close the basement door.

You need at least a return air on each zone. A proper system has a return air in each room.

John

Say what?!?!?!? :confused::confused:

The typical hvac system, at least in my area, has one return air duct per floor being conditioned, located centrally to the rooms on that floor. Each room has a feed trunk to condition the space, and if you look there should be a gap of about 1" under the door, this allows for air to be moved from the room whether the door is closed or not. I cannot recall of a single instance in either residential or commercial applications where supply and return vents are in every room.

Both levels have their own return vents, two on each level. The door does have an inch gap at the bottom to allow some air to pass, but if the door is closed, the air is really being pulled hard under there. I would assume this creates a pressure issue, and air would be pulled from all the openings around doors, windows, etc, from the outside?

Being a dual zone system, my thought is they should be fairly independent.

The typical hvac system, at least in my area, has one return air duct per floor being conditioned, located centrally to the rooms on that floor. Each room has a feed trunk to condition the space, and if you look there should be a gap of about 1" under the door, this allows for air to be moved from the room whether the door is closed or not. I cannot recall of a single instance in either residential or commercial applications where supply and return vents are in every room.

Even in the state of Florida where they have very relaxed codes you must have a return air in each bedroom.

The typical hvac system, at least in my area, has one return air duct per floor being conditioned, located centrally to the rooms on that floor. Each room has a feed trunk to condition the space, and if you look there should be a gap of about 1" under the door, this allows for air to be moved from the room whether the door is closed or not. I cannot recall of a single instance in either residential or commercial applications where supply and return vents are in every room.

Having a return and supply in as many rooms as possible allows for your equipment to run more efficient any day of the week in my opinion.
I lived and built homes all over the Northern Chicago land area for yrs. Most all newer homes in that area have returns in every room when possible.

Must be an east coast thing, because that's not the norm here on in the west. I've been in and around the trades for the past 25 years and have never seen it here.

Next thing you guys are gonna tell me is that you prefer side winders to worm drives. :eek::p;):D

HAHA not quite Spruce, I started out with a worm Drive's and never changed in 35 yrs. Ive been to Skill Corpotate Headquarters in Chicago, its quite a treat to look at the first worm saw invented.There monsters

If you go to the southern states they prefer the sidewinders,so do the tradesman in the Northern Eastern States....

I have a new home with a dual fuel, dual zone HVAC system, which supplies the main living level (zone 1) and a daylight basement (zone 2). They are seperated by a door at the top of the stairs. When the unit is supplying the main level, we have to leave the door open at least four or five inches, or it gets sucked closed with a bang! The air handler is using the basement returns to feed the air requirements.

I spoke to two seperate heating/cooling guys (from the same shop who installed the system) and both said that this is normal, that the air from both floors needs to mix. This makes sense I guess if I wanted to keep both floors conditioned, but the basement tends to stay at a comfortable temp, and we're down there rarely anyway. Seems to me this is an imbalanced system design. Am I correct, or am I the one imbalanced? :eek:
Your system is not balanced.
If they are saying the air from both floors need to mix --- well --- that is a riduculious answer. Good grief --- you have a 2 zone system -- the point is to condition each zone seperately. Otherwise, why have zone control in the first place ?
Then and again --- the crap information you're getting from those wing nuts is no surprise since it's those same wing nuts that installed the system.

Based on your information the system is a bad design.

Sounds to me with the lower level drawing more air into the return than the upper level -- you have poor heating/cooling in the upper level. Chances are your upper level isn't as comfortable as it should be since a large amount of conditioned air is being drawn out of that zone resulting in hot/cold spots. Not only will this affect your comfort but it also means your heating/cooling system is not running efficently as it should -- costing you more to condition your home.

A forced air system should never create a negative pressure condition within the home --- regardless if it's a single or multi-zone setup. This creates a dangerous situation where back drafting can occur with fuel fired combustion appliances --- resulting a build up of carbon monoxide in the home.

I'd also be interested in any thoughts on easily correcting this - maybe a simple pass-through register from the main level to the basement? The door in question is 90* from another door to our garage (they open into each other), which means making sure they don't bang into each other, so it would be nice to be able to close the basement door.

Thanks.

No one can see your setup over the internet to be able to say what exactly needs to be done to correct the issue. However , it sounds as though not much thought went into designing your system.

First thing that comes to mind is there too much return in the lower level and not enough for the upper level.
Sounds like they took the fast , easy and cheap route of calculating the distribution system and not considering all the variables to give you a properly designed sytem.

Chances are they used the square footage of each level and simply installed supplies and returns based soley on that. When in fact you may only need half of the return volume in the lower level based on the layout of the lower space , amount of conditioning , etc..

If your air delivery system ( or air handler ) is a constant volume single speed blower then it's a mater of ensuring properly balanced supply and return are in place based on the variables for each zone. Along with ensuring that static pressure is not affected by the state of each zone-- upsetting the balance.

With a variable speed blower it can be somewhat easier to regulate the air flow for zoned systems --- but ---- the supply and return still need to be balanced.

So , what's needed to correct your issue ?

It's time you called another HVAC professional who is knowledgeable with zoning forced air sytems to evaluate yor situation and come up with recommendations.
It may be redoing the supplies and return to properly balance the system.

Whether it's more of both in the upper level and less in the lower level or even a bypass to relieve static pressures it's hard to say sight unseen.

It"s not rocket science for HVAC professionals who know what they are doing to install a zoned system --- just some careful thought and planning.